In known manner, the shape of the mask in such an arrangement is such that the cut-off beam emitted by the headlamp is normalized. However, the cut-off effected in the light beam is relatively sharp and above the cut-off the light beam has a very feeble intensity, and in fact is practically zero.
FIG. 2 of the accompanying drawings shows a diagrammatic example of the distribution of light intensity in a lighting beam emitted by a known elliptical headlamp (representation of the isolux curves of the beam). As can be seen, the zone A situated above the cut-off of the light beam contains very little light.
The fact that the light beam emitted by such a headlamp has a very low intensity above the cut-off may be particularly annoying for a driver attempting to see road signs located at a high level, for example on motorway gantry supports.
Furthermore, it is a requirement of the statutory regulations that the lighting beam emitted by an automobile vehicle headlamp must have a certain intensity above the cut-off of the beam.
In order to increase the intensity of the light beam above its cut-off, it is proposed, for example in document G 90 00 395, that the convex lens comprises in a lower part situated below the optical axis of the headlamp (coincident with the axis of the convex lens) refraction striations which elevate part of the light beam reflected by the reflector over a predetermined angle so as to graze the upper edge of the mask interposed between the latter and the lens.
However such an arrangement is not entirely satisfactory.
It is an object of the present invention to provide a new type of headlamp for an automobile vehicle which emits a lighting beam having a light intensity above the cut-off which is of an acceptable level and complies with regulations, making it possible to illuminate signs located at a high level for the driver.